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Physiology 20: 152-161, 2005; doi:10.1152/physiol.00049.2004
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Physiology, Vol. 20, No. 3, 152-161, June 2005
© 2005 Int. Union Physiol. Sci./Am. Physiol. Soc.

REVIEW

Transgenic and Knockout Mice in Diabetes Research: Novel Insights into Pathophysiology, Limitations, and Perspectives

L. Plum1,2,3, F. T. Wunderlich1,3, S. Baudler1,3, W. Krone2,2 and J. C. Brüning1,3

1 Department of Mouse Genetics and Metabolism, Institute for Genetics;
2 Department of Internal Medicine II; and
3 Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany


   Abstract
 
Insulin resistance and type 2 diabetes are serious public health threats. Although enormous research efforts have been focused on the pathogenesis of these diseases, the underlying mechanisms remain only partly understood. Here we review mouse phenotypes resulting from inactivation of molecules responsible for the control of glucose metabolism that have led to novel insights into insulin action and the development of insulin resistance. In addition, more sophisticated strategies to manipulate genes in mice in the future are presented.


   Introduction
Top
 Introduction
Knockout Models with...
 Transgenic and Knockout Models...
 Future Perspectives
 Conclusions
 References
 
Type 2 diabetes mellitus is the most common endocrine disease, affecting ~5% of Western populations with steadily increasing incidence (77). Today, more than 18 million Americans (~6.3% of the U.S. population) suffer from diabetes, an important risk factor for cardiovascular disease, which is the main cause of death worldwide (43, 55). Diabetes is the most common cause of blindness among working-age adults, the most common cause of renal failure, and the sixth most common cause of death in the U.S. (99a). The rising prevalence of type 2 diabetes worldwide is mainly the consequence of the drastically increasing prevalence of obesity (35).

Epidemiological and twin studies have clearly indicated a genetic predisposition for the development of type 2 diabetes (38, 42, 74, 82), which is most likely of varying penetrance and of polygenic nature (38). It could be demonstrated that the fundamental dysfunction in type 2 diabetes is insulin resistance, which comprises both the failure of insulin to stimulate glucose uptake in skeletal muscle and adipose tissue and its inability to suppress hepatic glucose production sufficiently (71, 73). To define potential genetic defects, research over the past two decades has focused on the identification and characterization of molecules involved in the insulin-signaling pathway, and much of the current progress in our understanding of insulin action and insulin resistance has been made with the use of mouse models with genetic modifications in this and intercommunicating pathways (Table 1Go).


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  		Table 1. Summary of knockout and transgenic mouse models
 
Insulin exerts its diverse biological effects by binding to and activating the membrane-bound insulin receptor (IR), thereby initiating the insulin signal transduction cascade (for details, see http://stke.sciencemag.org/cgi/cm/CMP_12069). IRs are not only present in the classical insulin target tissues, i.e., adipose tissue, skeletal muscle, and liver, but are also widely expressed throughout the organism in tissues such as pancreas (45), the central nervous system (CNS) (72), lymphatic cells (11, 17), and kidney (6, 62). Signals initiated by the activated IR result in the diverse biological effects of insulin, such as the stimulation of glucose transport, the inhibition of gluconeogenesis, the stimulation of protein and lipid synthesis, and the regulation of gene transcription. Because the roles of many components of the signaling pathway were initially characterized in vitro, more recent research has focused on the analysis of insulin action in vivo by generating mice with targeted disruption of genes for these components. Since the pattern of inheritance of type 2 diabetes points to a disease of polygenic nature, not only single gene-deficient mice but also models with combined genetic disruptions have been created in an attempt to represent the polygenic nature of the disease. New techniques have also become available for conditional gene inactivation in mice. This is particularly helpful if conventional knockout of a gene results in embryonic lethality, preventing the analysis of gene function in the adult. Conditional mutagenesis enables the inactivation of a gene of interest in a specific tissue (92, 93, 99) or in a temporally controlled manner, thereby providing new insights into the contribution of a gene to a complex physiological phenotype such as insulin resistance.


   Knockout Models with Inactivation of Insulin-Signaling Molecules
Top
 Introduction
 Knockout Models with...
Transgenic and Knockout Models...
 Future Perspectives
 Conclusions
 References
 
The first knockout models of insulin resistance aimed at the disruption of major molecules in IR signaling. The successful generation of viable, heterozygous IR knockout mice showed that 50% of IR expression is sufficient for the maintenance of physiological blood glucose concentrations. In contrast, homozygous IR-deficient mice rapidly develop diabetic ketoacidosis and die within 3–7 days after birth (2, 49), showing the indispensability of IR for the control of glucose metabolism.

Skeletal muscle and insulin resistance
Because insulin resistance in skeletal muscle is one of the earliest detectable defects in type 2 diabetic patients, muscle-specific insulin receptor knockout (MIRKO) mice have been generated as a model for muscle-specific insulin resistance. MIRKO mice displayed elevated fat mass, serum triglycerides, and free fatty acids, indicating that insulin resistance in muscle contributes to the altered fat metabolism associated with type 2 diabetes (20). Additionally, Kim et al. (53) demonstrated that IR deficiency in muscle promotes redistribution of substrates to adipose tissue, thereby contributing to increased adiposity in MIRKO mice. Surprisingly, blood glucose, serum insulin, and glucose tolerance were normal in these mice, initially leading to the interpretation that tissues other than muscle are more essential for insulin-regulated glucose disposal than previously assumed. However, Zisman et al. (103) disrupted the gene for the glucose transporter 4 (Glut4), which mediates glucose transport in response to insulin, selectively in mouse muscle tissue. They found that Glut4-mediated glucose uptake in muscle was indeed essential for the maintenance of normal glucose homeostasis. Consistently, mice with a combined muscle-specific functional inactivation of IR and the closely related insulin-like growth factor receptor (IGF-1R) also display a complete type 2 diabetic phenotype, implicating a compensatory role of IGF-1R for mediating insulin’s stimulation of glucose transport via Glut4 in muscle (34).

The role of adipose tissue in muscle-specific IR deficiency was addressed in mice with a targeted inactivation of IR-mediated signaling in both muscle and adipose tissue (63). These mice did not become diabetic despite peripheral insulin resistance and a mild impairment of ß-cell function. Together, these data suggest that there may be a critical threshold in whole body insulin resistance that finally leads to a diabetic phenotype. Moreover, this insulin resistance might result in excessive demands on the pancreatic ß-cells to secrete insulin, leading to consecutive decompensation of these cells. Although dysfunction of the pancreatic ß-cell is undoubtedly rightly considered as an important defect in the pathogenesis of type 2 diabetes, its exact relationship to insulin resistance remained unclear.

Role of the ß-cell in impaired glucose tolerance
Mice with a specific disruption of the IR gene in ß-cells show a selective loss of insulin secretion in response to glucose and a progressive impairment of glucose tolerance (59), indicating that insulin stimulates its own secretion via IRs on ß-cells, thus playing an important functional role in glucose sensing by the pancreatic ß-cell. Therefore, defects in insulin signaling at the level of the ß-cell may contribute to the observed alterations in insulin secretion in type 2 diabetes. Interestingly, a ß-cell-specific IGF-1R knockout model also underscored a role for this receptor in the control of glucose-stimulated insulin secretion and glucose tolerance (60). The interplay between insulin resistance and insulin secretory defects has also been addressed by the generation of mice deficient for insulin receptor substrate 1 (IRS-1) and ß-cell glucokinase (GK) (98). The heterozygous ß-cell GK knockout is characterized by decreased insulin secretion in response to glucose (3), whereas IRS-1-deficient mice are insulin resistant but do not develop overt diabetes (1). In contrast to either individual mutation, the double-knockout mice developed a diabetic phenotype, demonstrating that the combination of individual minor defects in insulin action or insulin secretion can cause overt diabetes.

Insulin resistance in the brain
The liver-specific insulin receptor knockout (LIRKO) mouse, as expected, exhibits a dramatic phenotype with severe insulin resistance and progressive liver failure (75), mirroring the critical role of insulin signaling in liver for regulating glucose homeostasis and maintaining normal hepatic function. However, IRs and insulin-signaling proteins are not exclusively expressed in classic insulin target tissues; they are also widely distributed throughout the CNS. CNS-specific disruption of the IR gene (NIRKO) revealed an important role of IRs in the regulation of energy disposal, fuel metabolism, and reproduction (21). It has very recently been shown in conventional IR-deficient mice that combined restoration of IR function selectively in brain, liver, and pancreatic ß-cells rescues these mice from neonatal death, prevents diabetes in a majority of animals, and restores adipose tissue content, lifespan, and reproductive function. Interestingly, IR substitution either limited to brain or liver and pancreatic ß-cells was sufficient to prevent neonatal death but not lipatrophic diabetes, leading to the surprising finding that IR signaling in nontypical insulin target tissues like the brain seems to be crucial to maintain fuel homeostasis and prevent diabetes (84).

Disruption of IRSs
Aside from IR knockouts, various molecules of the signal transduction pathway initiated by IR have been disrupted, such as IRS-1, which was believed to be the principal substrate for the IR and IGF-1R. Mice deficient for IRS-1 exhibit impaired glucose tolerance and a decrease in insulin/IGF-1-stimulated glucose uptake in vivo and in vitro, thereby providing a mouse model of genetically determined insulin resistance (1, 89). Additionally, elevated blood pressure and plasma triglyceride levels were observed, as well as impaired endothelium-dependent vascular relaxation (1), indicating that insulin resistance plays an important role in the clustering of coronary risk factors leading to accelerated atherosclerosis. The residual insulin/IGF-1 action in IRS-1-deficient mice correlated with the existence of an alternative tyrosine-phosphorylated protein (IRS-2) (5, 85), which is also capable of activating the signaling cascade. Surprisingly, disruption of IRS-2 impaired peripheral insulin signaling and pancreatic ß-cell function, resulting in progressive deterioration of glucose homeostasis. This phenotype results from insulin resistance in liver and skeletal muscle and ß-cell dysfunction (57). Succeeding studies indicated tissue-specific functions for IRS-1 and IRS-2 in mediating the metabolic effects of insulin in vivo, IRS-1 having a major role in skeletal muscle and IRS-2 in liver, muscle, adipose tissue, pancreatic ß-cells, and reproductive tissue (22). Interestingly, mice with a double knockout of IRS-1 and the subsequently identified IRS-3 (65, 66) displayed a phenotype of early-onset severe lipatrophy associated with hyperglycemia, hyperinsulinemia, and decreased plasma levels of the anorexigenic hormone leptin. The IRS-1/IRS-3 double-knockout phenotype in mice (64) might mimic the situation in humans better than the single IRS-1 knockout, since Bjornholm et al. (12) demonstrated that no functional IRS-3 homolog is present in humans that could compensate for defects in IRS-1 signaling.

The concept that several subclinical genetic alterations in insulin action can synergize to result in overt diabetes was tested in mice double heterozygous for IR and IRS-1 alleles with a ~50% reduction in expression of either protein (19). In these mice, the combined genetic defects led to aggravation of insulin resistance with 5- to 50-fold elevated plasma insulin levels and respective ß-cell hyperplasia, and ~40% of the animals developed overt diabetes at the age of 4–6 mo. This mouse model of type 2 diabetes, in which diabetes arises in an age-dependent manner from the interaction between two genetically determined, subclinical defects in the insulin-signaling cascade, demonstrates the important role of epistatic interactions in the pathogenesis of common diseases with non-Mendelian genetics. Moreover, this model has been used successfully to identify further modifying C57BL/6 loci regulating insulin sensitivity (4).

The role of adipose tissue
The strong association between the world-wide epidemic of obesity and dramatically increasing prevalence of insulin resistance and type 2 diabetes has prompted recent research to focus on the mechanisms linking adipose tissue to whole body insulin sensitivity, ß-cell function, and overall glucose metabolism. Newborn mice with IR deficiency show a marked reduction in white adipose tissue mass, pointing to a role for IR in the regulation of adipocyte growth and differentiation (2, 49). Mice with an adipose tissue-specific knockout of the IR (FIRKO) also display a reduced fat mass, loss of the normal correlation of plasma leptin and body weight, and protection against both obesity and obesity-related glucose intolerance (13). Interestingly, they also exhibit an 18% extended lifespan (14). Strikingly, whereas adipocytes of control mice exhibit a bell-shaped size distribution, adipocytes of FIRKO mice demerge into groups of small and large cells. Interestingly, these differently sized cells also show different expression of fatty acid synthase and the transcription factors CCAAT enhancer binding protein (C/EBP)-{alpha} as well as sterol regulatory element-binding protein 1 (SREBP1) (15, 16). Thus inactivation of the IR revealed a previously unrecognized heterogeneity of adipose tissue. Consistent with the phenotype of Glut4-null mice, which display a depletion of fat stores (51), the selective disruption of Glut4 in adipose tissue caused an impaired glucose transport, followed by development of insulin resistance (1a). These data clearly assign adipocytes an important role in lipid storage, development of obesity, and regulation of glucose homeostasis.

Recent studies have identified a family of transcription factors, the Foxos, as effectors of insulin signaling in diverse cell types (reviewed in Ref. 54). Foxo1 is present in the nucleus, where it activates gene transcription; upon insulin stimulation, the transcription factor is phosphorylated and excluded from the nucleus, thus interfering with its function as a transcriptional activator. One example of Foxo1-mediated insulin action is the insulin-induced suppression of gluconeogenesis, because unphosphorylated Foxo1 induces transcription of glucose-6-phosphatase, a key gluconeogenic enzyme (80). Double-heterozygous Foxo1/IR-deficient mice exhibited improved insulin sensitivity compared with insulin-resistant heterozygous IR knockouts (81). This phenomenon is the consequence of a complex mechanism involving decreased glucose production, increased ß-cell performance, and expression of insulin-sensitive genes in adipose tissue (reviewed in Ref. 32). Puigserver et al. (90) have shown that Foxo1 is coactivated by peroxisome proliferator-activated receptor (PPAR)-{gamma} coactivator-1{alpha} (PGC-1{alpha}) in a manner that is inhibited by insulin stimulation, thereby linking insulin-mediated regulation of transcription to PGC-1.


   Transgenic and Knockout Models in Other Pathways Regulating Insulin Action
Top
 Introduction
 Knockout Models with...
 Transgenic and Knockout Models...
Future Perspectives
 Conclusions
 References
 
Inactivation of PPARs
It has been shown that the abnormal accumulation of lipids in tissues other than adipose adversely affects insulin sensitivity (27, 52, 86, 87), indicating a complex system for the comprehensive control of lipid and glucose homeostasis. The key coordinators in this metabolic axis are members of the nuclear hormone receptor superfamily (31). Among those, PPARs respond to small lipid agents (28), e.g., dietary fatty acids, and contribute a key mechanism in the regulation of lipid and glucose metabolism (reviewed in Ref. 91). The important physiological role of the PPARs, i.e., PPAR-{alpha}, -ß/{delta}, and -{gamma}, was deduced from findings identifying the PPARs as primary targets of two key classes of synthetic compounds that have been used in the successful treatment of diabetes and dyslipidemia. In particular, thiazolidinedione (TZD) insulin sensitizers are potent and specific PPAR-{gamma} ligands and activators (68). Fibrates have predominant activity as PPAR-{alpha} agonists, favorably affecting serum lipid levels (78). Diverse knockout models have been created to study the function of the single PPAR isoforms in vivo.

Consistent with the concept that PPAR-{alpha} is the member of the PPAR family that mediates cellular lipid utilization, pharmacological inhibition of cellular fatty acid flux in mice lacking PPAR-{alpha} caused massive hepatic and cardiac lipid accumulation, hypoglycemia, and death in 100% of male and 25% of female animals, demonstrating a pivotal role for PPAR-{alpha} in lipid and glucose homeostasis in vivo. Nevertheless, there was no major phenotypic defect detectable in PPAR-{alpha} knockouts without pharmacological challenge (26, 67). Muoio et al. showed that skeletal muscle of PPAR-{alpha}-deficient mice exhibited only minor changes in fatty acid homeostasis, and even mRNA expression of known PPAR-{alpha} target genes in muscle tissue was not significantly affected (79). They proposed that this finding might be explained by high levels of PPAR-ß/{delta} compensating for the lack of PPAR-{alpha}, suggesting redundancy in the functions of PPARs as transcriptional regulators of fatty acid homeostasis.

In contrast to the embryonic lethality of homozygous PPAR-{gamma} knockouts (8), mice deficient only for the PPAR-{gamma}2 isoform survived, exhibiting an overall reduction in white adipose tissue, less lipid accumulation, and decreased expression of adipogenic genes in adipose tissue (102). Consistently, embryonic fibroblasts of PPAR-{gamma}2 knockouts showed a dramatically reduced capacity for adipogenesis in vitro (102). In addition, insulin sensitivity was impaired in these mice, with decreased expression of IRS-1 and Glut4 in skeletal muscle, but TZDs were able to normalize this insulin resistance (102). In contrast, heterozygous PPAR-{gamma} knockouts show reduced disposition to insulin resistance (56). Strikingly, this phenotype is blunted by treatment with a synthetic PPAR-{gamma} ligand of the TSD class, indicating that optimal levels of PPAR-{gamma} activity are crucial for its beneficial effects (101). To address these obvious incongruities, PPAR-{gamma} has been selectively disrupted in liver, adipose tissue, and muscle (31, 39, 46, 47, 83). Briefly, although adipose tissue appears to be the main site of TZD action, the conditional knockouts highlight important functions for muscle and liver PPAR-{gamma} in the control of body composition and insulin sensitivity. PPAR-{gamma} deficiency in adipose tissue leads to progressive loss of fat, hyperlipidemia, fatty liver, and accompanying hepatic insulin resistance (46). The mice can maintain normal whole body glucose homeostasis and normal insulin sensitivity only as long as some adipose tissue is present. These studies identify a molecular link between blood glucose homeostasis and lipid metabolism, providing a genetic basis for the observed phenotypic correlation between obesity and type 2 diabetes mellitus.

Lessons from other models
Besides PPAR-{gamma}, C/EBP-{alpha} is also a major regulator of adipocyte differentiation. C/EBP-null mice fail to develop white adipose tissue and to store hepatic glycogen, leading to death from hypoglycemia within 8 h after birth (100). In cells ectopically expressing PPAR-{gamma}, the development of insulin-responsive glucose uptake in vitro correlates with C/EBP-{alpha} expression, suggesting that although PPAR-{gamma} is sufficient to trigger the adipogenic program, C/EBP-{alpha} is required for establishment of insulin-sensitive glucose transport (29). Consistent with these findings, Cariou et al. (23) demonstrated that adipocyte hyperplasia observed in MIRKO mice is accompanied by increased expression of C/EBP-{alpha}, confirming the importance of molecules that alter adipose tissue mass ("WAT plasticity") in the maintenance of whole body insulin sensitivity.

SREBP-1 belongs to a family of transcription factors involved in cholesterol and fatty acid metabolism (18), and it has been suggested that it mediates the effects of insulin on hepatic genes involved in glucose and lipid metabolism (7, 37, 48, 96, 97). Overexpression of SREBP-1c specifically in the liver of diabetic mice markedly decreased hyperglycemia due to increased expression of glucokinase and lipogenic enzyme gene, and it repressed expression of phosphoenolpyruvate carboxykinase, a key enzyme of the gluconeogenic pathway, indicating a major role of SREBP-1c in the control of glucose homeostasis by insulin (10).

On the basis of these data, the emerging picture is of a complex interaction of IR-mediated signaling and pathways involving nuclear hormone receptors, physiologically linking systemic glucose homeostasis, lipid metabolism, and adipocyte biology.


   Future Perspectives
Top
 Introduction
 Knockout Models with...
 Transgenic and Knockout Models...
 Future Perspectives
Conclusions
 References
 
The employment of even more sophisticated strategies in conditional gene targeting may overcome these limitations in the future. Conditional inactivation of genes is mainly achieved by the Cre-loxP system. The bacteriophage P1-derived Cre recombinase excises a segment of genomic DNA, which has been flanked with specific recognition sites ("loxP sites") by genetic engineering. The Cre recombinase gene and additional DNA elements that control its expression are also introduced into the genome of the host animal. The onset of the conditional inactivation of the gene can be triggered at specific developmental stages by a temporally controlled Cre expression (70). Presently, the inducible systems existing to control Cre recombinase activity are either at the transcriptional or the posttranslational level. Cell type-specific transcriptional control of Cre can be achieved by the tet systems, in which the activity of almost silent gene promoters can be enhanced manyfold through binding of inducer proteins that are regulated by the antibiotics tetracycline or doxycycline (40). In the tet-off system, transcription is abrogated by administration of doxycycline, which upon binding to the synthetic transcription factor tetracycline-controlled transcriptional activator (tTA) prevents binding of tTA to the gene-regulatory promoter/operator element tetO and transcription of the target gene, here the Cre recombinase gene (40). In the complementary tet-on system, transcription is activated only in the presence of doxycycline, since the reverse tetracycline controlled activator rtTA requires doxycycline binding to activate transcription (41) (FIGURE 1AGo). In both systems, the genomic integration site of the tetO promoter driving the transgene of interest is critical. When endogenous enhancers are located in close environment to the tetO promoter, the promoter can be activated even in the absence of the active transcriptional activators, resulting in leaky expression of the transgene. A recently described integration site for the tetO promoter offers an alternative approach. A bidirectional tetO promoter (9) in transgenic LC-1 mice (94) drives the expression of Cre and luciferase, respectively, and can be tightly regulated by transactivating units of both the tet-on and tet-off systems.



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  		FIGURE 1. Inducible systems for conditional inactivation of genes
A: when employing the tet-on system, transcription of Cre recombinase is induced by administration of doxycycline (Dox), which binds to the reverse tetracycline-controlled activator (rtTA). B: when Cre is fused to the ligand-binding domain (LBD) of the estrogen receptor (ER), the recombinase is inactivated by heat shock proteins (HSPs) bound to the ERLBD. After addition of tamoxifen (Tam), the fusion protein becomes activated and can mediate excision of a loxP-flanked target gene in the nucleus.

 
In the posttranslational regulation, a fusion protein between Cre and the ligand-binding domain (LBD) of a steroid hormone receptor can be expressed from any given cell type-specific promoter. In the absence of steroid hormone, the LBDs are bound by heat shock proteins, which inactivate recombinase activity, presumably by steric hindrance. After administration of the steroid hormone, the fusion protein becomes activated and can mediate excision of a loxP-flanked target gene in the nucleus (FIGURE 1BGo). To generate a posttranslational system of Cre fused to the LBD of the estrogen receptor (ER), single-amino-acid substitutions were introduced in the ER-LBD to prevent its activation by the endogenous hormone 17ß-estradiol (E2) but maintain its binding capacities for synthetic steroids such as 4-hydoxytamoxifen (33). During recent years, numerous transgenic mouse strains were generated that express the Cre fusion protein ubiquitously (95) or restricted to several tissues, for example muscle or brain (25, 36, 58, 69). Crossing these inducible Cre mouse strains to mice carrying conditional alleles of insulin-signaling molecules allows the role of those molecules in different tissues to be distinguished, as for example the effect of insulin action in ß-cell development vs. roles in the insulin secretion pathway in adult mice.

However, conditional mutagenesis also has its limitations. The generation of loxP-flanked alleles is often time consuming, or of limited value, due to the existence of multiple copies of the gene and/or pseudogenes in the genome in which undesired targeting events can occur. To overcome such limitations, the recently described RNA interference (RNAi) method may offer feasible alternatives (22). Small double-stranded hairpin RNA molecules (shRNAs) complementary to a part of the messenger RNA of the gene of interest are processed by the enzyme Dicer into small interfering (si)RNAs, that are 19–23 nucleotides in length (44). These siRNAs become unwound by an RNA helicase and subsequently incorporated as single-stranded siRNAs into the RISC complex that guides this complex to the mRNA, resulting in its degradation. Specific shRNAs directed against any gene of interest can be delivered directly as synthetic oligonucleotides to cultured cells (30), or they can be expressed in transgenic mice under the control of RNA polymerase III promoters such as the U6 and H1 (24). Mice expressing an shRNA transgene display in some cases the identical phenotype to those carrying a null mutation in the target gene (61). However, the efficiency of this so-called "gene knockdown" has to be maximized for every gene and may be dependent on factors such as the sequence of the processed siRNA, the cell type in which the mRNA should be degraded, and the accessibility of the siRNA to the mRNA due to secondary structures (76). Ongoing investigations in the RNAi field like the conditional expression of shRNAs using the Cre/loxP system (50) will provide a useful and fast approach in the toolkit of reverse genetics.


   Conclusions
Top
 Introduction
 Knockout Models with...
 Transgenic and Knockout Models...
 Future Perspectives
 Conclusions
References
 
New concepts for the molecular basis of insulin action and insulin resistance have emerged thanks to the availability of techniques for conditional mutagenesis, leading to the view that insulin resistance of various classical and nonclassical target tissues can combine to cause the complex phenotype of insulin resistance and type 2 diabetes. Nevertheless, the conclusions derived from these experiments are limited by the fact that, even in the tissue- and cell type-specific knockouts, gene inactivation is effective throughout development. Therefore, 1) there are probably compensatory mechanisms for the loss of individual proteins, and 2) it may be difficult to distinguish phenotypes arising from developmental defects from those resulting from impaired signaling.

In summary, mouse models with single genetic defects can yield important information about the action of insulin in glucose metabolism but may not always match the human disease states. Thus it is critical that new, relevant animal models employing more sophisticated strategies for gene inactivation be developed to extend our understanding of the mechanisms underlying type 2 diabetes and obesity.


   Acknowledgments
 
We thank Prof. Jonathan C. Howard and Dr. Susanna Freude for help with the preparation and the critical reading of the manuscript.

This work was supported by a grant from the Cologne Fortune Program (to L. Plum) and from the Deutsche Forschungsgemeinschaft and the Center for Molecular Medicine Cologne to J. C. Brüning.


   References
Top
 Introduction
 Knockout Models with...
 Transgenic and Knockout Models...
 Future Perspectives
 Conclusions
 References
 

  1. Abe H, Yamada N, Kamata K, Kuwaki T, Shimada M, Osuga J, Shionoiri F, Yahagi N, Kadowaki T, Tamemoto H, Ishibashi S, Yazaki Y, and Makuuchi M. Hypertension, hypertriglyceridemia, and impaired endothelium-dependent vascular relaxation in mice lacking insulin receptor substrate-1. J Clin Invest 101: 1784–1788, 1998.[ISI][Medline]
  2. Abel ED, Peroni O, Kim JK, Kim YB, Boss O, Hadro E, MinnemannT, Shulman GI, and Kahn BB. Adipose-selective targeting of the GLUT4 gene impairs insulin action in muscle and liver. Nature 409: 729–733, 2001.[CrossRef][Medline]
  3. Accili D, Drago J, Lee EJ, Johnson MD, Cool MH, Salvatore P, Asico LD, Jose PA, Taylor SI, and Westphal H. Early neonatal death in mice homozygous for a null allele of the insulin receptor gene. Nat Genet 12: 106–109, 1996.[CrossRef][ISI][Medline]
  4. Aizawa T, Asanuma N, Terauchi Y, Suzuki N, Komatsu M, Itoh N, Nakabayashi T, Hidaka H, Ohnota H, Yamauchi K, Yasuda K, Yazaki Y, Kadowaki T, and Hashizume K. Analysis of the pancreatic ß cell in the mouse with targeted disruption of the pancreatic ß cell-specific glucokinase gene. Biochem Biophys Res Commun 229: 460–465, 1996.[CrossRef][Medline]
  5. Almind K, Kulkarni RN, Lannon SM, and Kahn CR. Identification of interactive loci linked to insulin and leptin in mice with genetic insulin resistance. Diabetes 52: 1535–1543, 2003.[Abstract/Free Full Text]
  6. Araki E, Lipes MA, Patti ME, Bruning JC, Haag B 3rd, Johnson RS, and Kahn CR. Alternative pathway of insulin signalling in mice with targeted disruption of the IRS-1 gene. Nature 372: 186–190, 1994.[CrossRef][Medline]
  7. Arnqvist HJ, Ballermann BJ, and King GL. Receptors for and effects of insulin and IGF-I in rat glomerular mesangial cells. Am J Physiol Cell Physiol 254: C411–C416, 1988.[Abstract/Free Full Text]
  8. Azzout-Marniche D, Becard D, Guichard C, Foretz M, Ferre P, and Foufelle F. Insulin effects on sterol regulatory-element-binding protein-1c (SREBP-1c) transcriptional activity in rat hepatocytes. Biochem J 350: 389–393, 2000.[CrossRef][Medline]
  9. Barak Y, Nelson MC, Ong ES, Jones YZ, Ruiz-Lozano P, Chien KR, Koder A, and Evans RM. PPAR {gamma} is required for placental, cardiac, and adipose tissue development. Mol Cell 4: 585–595, 1999.[CrossRef][ISI][Medline]
  10. Baron U, Freundlieb S, Gossen M, and Bujard H. Co-regulation of two gene activities by tetracycline via a bidirectional promoter. Nucleic Acids Res 23: 3605–3606, 1995.[Free Full Text]
  11. Becard D, Hainault I, Azzout-Marniche D, Bertry-Coussot L, Ferre P, and Foufelle F. Adenovirus-mediated overexpression of sterol regulatory element binding protein-1c mimics insulin effects on hepatic gene expression and glucose homeostasis in diabetic mice. Diabetes 50: 2425–2430, 2001.[Abstract/Free Full Text]
  12. Berman JS and Center DM. Chemotactic activity of porcine insulin for human T lymphocytes in vitro. J Immunol 138: 2100–2103, 1987.[Abstract]
  13. Bjornholm M, He AR, Attersand A, Lake S, Liu SC, Lienhard GE, Taylor S, Arner P, and Zierath JR. Absence of functional insulin receptor substrate-3 (IRS-3) gene in humans. Diabetologia 45: 1697–1702, 2002.[CrossRef][ISI][Medline]
  14. Bluher M, Michael MD, Peroni OD, Ueki K, Carter N, Kahn BB, and Kahn CR. Adipose tissue selective insulin receptor knockout protects against obesity and obesity-related glucose intolerance. Dev Cell 3: 25–38, 2002.[CrossRef][ISI][Medline]
  15. Bluher M, Kahn BB, and Kahn CR. Extended longevity in mice lacking the insulin receptor in adipose tissue. Science 299: 572–574, 2003.[Abstract/Free Full Text]
  16. Bluher M, Patti ME, Gesta S, Kahn BB, and Kahn CR. Intrinsic heterogeneity in adipose tissue of fat-specific insulin receptor knock-out mice is associated with differences in patterns of gene expression. J Biol Chem 279: 31891–31901, 2004.[Abstract/Free Full Text]
  17. Bluher M, Wilson-Fritch L, Leszyk J, Laustsen PG, Corvera S, and Kahn CR. Role of insulin action and cell size on protein expression patterns in adipocytes. J Biol Chem 279: 31902–31909, 2004.[Abstract/Free Full Text]
  18. Braciale VL, Gavin JR 3rd, and Braciale TJ. Inducible expression of insulin receptors on T lymphocyte clones. J Exp Med 156: 664–669, 1982.[Abstract/Free Full Text]
  19. Brown MS and Goldstein JL. The SREBP pathway: regulation of cholesterol metabolism by proteolysis of a membrane-bound transcription factor. Cell 89: 331–340, 1997.[CrossRef][ISI][Medline]
  20. Bruning JC, Winnay J, Bonner-Weir S, Taylor SI, Accili D, and Kahn CR. Development of a novel polygenic model of NIDDM in mice heterozygous for IR and IRS-1 null alleles. Cell 88: 561–572, 1997.[CrossRef][ISI][Medline]
  21. Bruning JC, Michael MD, Winnay JN, Hayashi T, Horsch D, Accili D, Goodyear LJ, and Kahn CR. A muscle-specific insulin receptor knockout exhibits features of the metabolic syndrome of NIDDM without altering glucose tolerance. Mol Cell 2: 559–569, 1998.[CrossRef][ISI][Medline]
  22. Bruning JC, Gautam D, Burks DJ, Gillette J, Schubert M, Orban PC, Klein R, Krone W, Muller-Wieland D, and Kahn CR. Role of brain insulin receptor in control of body weight and reproduction. Science 289: 2122–2125, 2000.[Abstract/Free Full Text]
  23. Burks DJ, de Mora JF, Schubert M, Withers DJ, Myers MG, Towery HH, Altamuro SL, Flint CL, and White MF. IRS2 pathways integrate female reproduction and energy homeostasis. Nature 407: 377–382, 2000.[CrossRef][Medline]
  24. Cariou B, Postic C, Boudou P, Burcelin R, Kahn CR, Girard J, Burnol AF, and Mauvais-Jarvis F. Cellular and molecular mechanisms of adipose tissue plasticity in muscle insulin receptor knockout mice. Endocrinology 145: 1926–1932, 2004.[Abstract/Free Full Text]
  25. Carmell MA, Zhang L, Conklin DS, Hannon GJ, and Rosenquist TA. Germline transmission of RNAi in mice. Nat Struct Biol 10: 91–92, 2003.[CrossRef][ISI][Medline]
  26. Casanova E, Fehsenfeld S, Lemberger T, Shimshek DR, Sprengel R, and Mantamadiotis T. ER based double iCre fusion protein allows partial recombination in forebrain. Genesis 34: 208–214, 2002.[CrossRef][ISI][Medline]
  27. Djouadi F, Weinheimer CJ, Saffitz JE, Pitchford C, Bastin J, Gonzalez FJ, and Kelly DP. A gender-related defect in lipid metabolism and glucose homeostasis in peroxisome proliferator-activated receptor {alpha}-deficient mice. J Clin Invest 102: 1083–1091, 1998.[ISI][Medline]
  28. Dresner A, Laurent D, Marcucci M, Griffin ME, Dufour S, Cline GW, Slezak LA, Andersen DK, Hundal RS, Rothman DL, Petersen KF, and Shulman GI. Effects of free fatty acids on glucose transport and IRS-1-associated phosphatidylinositol 3-kinase activity. J Clin Invest 103: 253–259, 1999.[ISI][Medline]
  29. Dreyer C, Krey G, Keller H, Givel F, Helftenbein G, and Wahli W. Control of the peroxisomal ß-oxidation pathway by a novel family of nuclear hormone receptors. Cell 68: 879–887, 1992.[CrossRef][ISI][Medline]
  30. El-Jack AK, Hamm JK, Pilch PF, and Farmer SR. Reconstitution of insulin-sensitive glucose transport in fibroblasts requires expression of both PPAR{gamma} and C/EBP{alpha}. J Biol Chem 274: 7946–7951, 1999.[Abstract/Free Full Text]
  31. Elbashir SM, Harborth J, Weber K, and Tuschl T. Analysis of gene function in somatic mammalian cells using small interfering RNAs. Methods 26: 199–213, 2002.[CrossRef][ISI][Medline]
  32. Evans RM, Barish GD, and Wang YX. PPARs and the complex journey to obesity. Nat Med 10: 355–361, 2004.[CrossRef][ISI][Medline]
  33. Farmer SR. The forkhead transcription factor Foxo1: a possible link between obesity, and insulin resistance. Mol Cell 11: 6–8, 2003.[CrossRef][Medline]
  34. Feil R, Wagner J, Metzger D, and Chambon P. Regulation of Cre recombinase activity by mutated estrogen receptor ligand-binding domains. Biochem Biophys Res Commun 237: 752–757, 1997.[CrossRef][ISI][Medline]
  35. Fernandez AM, Kim JK, Yakar S, Dupont J, Hernandez-Sanchez C, Castle AL, Filmore J, Shulman GI, and Le Roith D. Functional inactivation of the IGF-I and insulin receptors in skeletal muscle causes type 2 diabetes. Genes Dev 15: 1926–1934, 2001.[Abstract/Free Full Text]
  36. Ford ES, Giles WH, and Dietz WH. Prevalence of the metabolic syndrome among U.S. adults: findings from the third National Health and Nutrition Examination Survey. JAMA 287: 356–359, 2002.[Abstract/Free Full Text]
  37. Forde A, Constien R, Grone HJ, Hammerling G, and Arnold B. Temporal Cre-mediated recombination exclusively in endothelial cells using Tie2 regulatory elements. Genesis 33: 191–197, 2002.[CrossRef][ISI][Medline]
  38. Foretz M, Pacot C, Dugail I, Lemarchand P, Guichard C, Le Liepvre X, Berthelier-Lubrano C, Spiegelman B, Kim JB, Ferre P, and Foufelle F. ADD1/SREBP1c is required in the activation of hepatic lipogenic gene expression by glucose. Mol Cell Biol 19: 3760–3768, 1999.[Abstract/Free Full Text]
  39. Froguel P, Velho G, Passa P, and Cohen D. Genetic determinants of type 2 diabetes mellitus: lessons learned from family studies. Diabetes Metab 19: 1–10, 1993.
  40. Gavrilova O, Haluzik M, Matsusue K, Cutson JJ, Johnson L, Dietz KR, Nicol CJ, Vinson C, Gonzalez FJ, and Reitman ML. Liver peroxisome proliferator-activated receptor {gamma} contributes to hepatic steatosis, triglyceride clearance, and regulation of body fat mass. J Biol Chem 278: 34268–34276, 2003.[Abstract/Free Full Text]
  41. Gossen M and Bujard H. Tight control of gene expression in mammalian cells by tetracycline-responsive promoters. Proc Natl Acad Sci USA 89: 5547–5551, 1992.[Abstract/Free Full Text]
  42. Gossen M, Freundlieb S, Bender G, Muller G, Hillen W, and Bujard H. Transcriptional activation by tetracyclines in mammalian cells. Science 268: 1766–1769, 1995.[Abstract/Free Full Text]
  43. Guillausseau PJ, Tielmans D, Virally-Monod M, and Assayag M. Diabetes: from phenotypes to genotypes. Diabetes Metab 23, Suppl 2: 14–21, 1997.[Medline]
  44. Haffner SM, Lehto S, Ronnemaa T, Pyorala K, and Laakso M. Mortality from coronary heart disease in subjects with type 2 diabetes and in nondiabetic subjects with and without prior myocardial infarction. N Engl J Med 339: 229–234, 1998.[Abstract/Free Full Text]
  45. Hannon GJ. Interference RNA. Nature 418: 244–251, 2002.[CrossRef][Medline]
  46. Harbeck MC, Louie DC, Howland J, Wolf BA, and Rothenberg PL. Expression of insulin receptor mRNA and insulin receptor substrate 1 in pancreatic islet ß-cells. Diabetes 45: 711–717, 1996.[Abstract]
  47. He W, Barak Y, Hevener A, Olson P, Liao D, Le J, Nelson M, Ong E, Olefsky JM, and Evans RM. Adipose-specific peroxisome proliferator-activated receptor {gamma} knockout causes insulin resistance in fat and liver but not in muscle. Proc Natl Acad Sci USA 100: 15712–15717, 2003.[Abstract/Free Full Text]
  48. Hevener AL, He W, Barak Y, Le J, Bandyopadhyay G, Olson P, Wilkes J, Evans RM, and Olefsky J. Muscle-specific Pparg deletion causes insulin resistance. Nat Med 9: 1491–1497, 2003.[CrossRef][ISI][Medline]
  49. Horton JD, Bashmakov Y, Shimomura I, and Shimano H. Regulation of sterol regulatory element binding proteins in livers of fasted and refed mice. Proc Natl Acad Sci USA 95: 5987–5992, 1998.[Abstract/Free Full Text]
  50. Joshi RL, Lamothe B, Cordonnier N, Mesbah K, Monthioux E, Jami J, and Bucchini D. Targeted disruption of the insulin receptor gene in the mouse results in neonatal lethality. EMBO J 15: 1542–1547, 1996.[ISI][Medline]
  51. Kasim V, Miyagishi M, and Taira K. Control of siRNA expression using the Cre-loxP recombination system. Nucleic Acids Res 32: e66, 2004.[Abstract/Free Full Text]
  52. Katz EB, Stenbit AE, Hatton K, DePinho R, and Charron MJ. Cardiac and adipose tissue abnormalities but not diabetes in mice deficient in GLUT4. Nature 377: 151–155, 1995.[CrossRef][Medline]
  53. Kim JK, Fillmore JJ, Chen Y, Yu C, Moore IK, Pypaert M, Lutz EP, Kako Y, Velez-Carrasco W, Goldberg IJ, Breslow JL, and Shulman GI. Tissue-specific overexpression of lipoprotein lipase causes tissue-specific insulin resistance. Proc Natl Acad Sci USA 98: 7522–7527, 2001.[Abstract/Free Full Text]
  54. Kim JK, Zisman A, Fillmore JJ, Peroni OD, Kotani K, Perret P, Zong H, Dong J, Kahn CR, Kahn BB, and Shulman GI. Glucose toxicity and the development of diabetes in mice with muscle-specific inactivation of GLUT4. J Clin Invest 108: 153–160, 2001.[CrossRef][ISI][Medline]
  55. Kops GJ and Burgering BM. Forkhead transcription factors: new insights into protein kinase B (c-akt) signaling. J Mol Med 77: 656–665, 1999.[CrossRef][ISI][Medline]
  56. Krone W and Meinertz T. Metabolic syndrome as a cardiovascular risk factor. Herz 20: 2–4, 1995.[Medline]
  57. Kubota N, Terauchi Y, Miki H, Tamemoto H, Yamauchi T, Komeda K, Satoh S, Nakano R, Ishii C, Sugiyama T, Eto K, Tsubamoto Y, Okuno A, Murakami K, Sekihara H, Hasegawa G, Naito M, Toyoshima Y, Tanaka S, Shiota K, Kitamura T, Fujita T, Ezaki O, Aizawa S, Kadowaki T, and ????. PPAR {gamma} mediates high-fat diet-induced adipocyte hypertrophy and insulin resistance. Mol Cell 4: 597–609, 1999.[CrossRef][ISI][Medline]
  58. Kubota N, Tobe K, Terauchi Y, Eto K, Yamauchi T, Suzuki R, Tsubamoto Y, Komeda K, Nakano R, Miki H, Satoh S, Sekihara H, Sciacchitano S, Lesniak M, Aizawa S, Nagai R, Kimura S, Akanuma Y, Taylor SI, and Kadowaki T. Disruption of insulin receptor substrate 2 causes type 2 diabetes because of liver insulin resistance and lack of compensatory ß-cell hyperplasia. Diabetes 49: 1880–1889, 2000.[Abstract]
  59. Kuhbandner S, Brummer S, Metzger D, Chambon P, Hofmann F, and Feil R. Temporally controlled somatic mutagenesis in smooth muscle. Genesis 28: 15–22, 2000.[CrossRef][ISI][Medline]
  60. Kulkarni RN, Bruning JC, Winnay JN, Postic C, Magnuson MA, and Kahn CR. Tissue-specific knockout of the insulin receptor in pancreatic ß cells creates an insulin secretory defect similar to that in type 2 diabetes. Cell 96: 329–339, 1999.[CrossRef][ISI][Medline]
  61. Kulkarni RN, Holzenberger M, Shih DQ, Ozcan U, Stoffel M, Magnuson MA, and Kahn CR. ß-cell-specific deletion of the Igf1 receptor leads to hyperinsulinemia and glucose intolerance but does not alter ß-cell mass. Nat Genet 31: 111–115, 2002.[ISI][Medline]
  62. Kunath T, Gish G, Lickert H, Jones N, Pawson T, and Rossant J. Transgenic interference in ES RNA cell-derived embryos recapitulates a genetic null phenotype. Nat Biotechnol 21: 559–561, 2003.[CrossRef][ISI][Medline]
  63. Kurokawa K, Silverblatt FJ, Klein KL, Wang MS, and Lerner RL. Binding of 125I insulin to the isolated glomeruli of rat kidney. J Clin Invest 64: 1357–1364, 1979.[Medline]
  64. Lauro D, Kido Y, Castle AL, Zarnowski MJ, Hayashi H, Ebina Y, and Accili D. Impaired glucose tolerance in mice with a targeted impairment of insulin action in muscle and adipose tissue. Nat Genet 20: 294–298, 1998.[CrossRef][ISI][Medline]
  65. Laustsen PG, Michael MD, Crute BE, Cohen SE, Ueki K, Kulkarni RN, Keller SR, Lienhard GE, and Kahn CR. Lipoatrophic diabetes in Irs1(–/–)/Irs3(–/–) double knockout mice. Genes Dev 16: 3213–3222, 2002.[Abstract/Free Full Text]
  66. Lavan BE, Fantin VR, Chang ET, Lane WS, Keller SR, and Lienhard GE. A novel 160-kDa phosphotyrosine protein in insulin-treated embryonic kidney cells is a new member of the insulin receptor substrate family. J Biol Chem 272: 21403–21407, 1997.[Abstract/Free Full Text]
  67. Lavan BE, Lane WS, and Lienhard GE. The 60-kDa phosphotyrosine protein in insulin-treated adipocytes is a new member of the insulin receptor substrate family. J Biol Chem 272: 11439–11443, 1997.[Abstract/Free Full Text]
  68. Lee SS, Pineau T, Drago J, Lee EJ, Owens JW, Kroetz DL, Fernandez-Salguero PM, Westphal H, and Gonzalez FJ. Targeted disruption of the alpha isoform of the peroxisome proliferator-activated receptor gene in mice results in abolishment of the pleiotropic effects of peroxisome proliferators. Mol Cell Biol 15: 3012–3022, 1995.[Abstract]
  69. Lehmann JM, Moore LB, Smith-Oliver TA, Wilkison WO, Willson TM, and Kliewer SA. An antidiabetic thiazolidinedione is a high affinity ligand for peroxisome proliferator-activated receptor {gamma} (PPAR {gamma}). J Biol Chem 270: 12953–12956, 1995.[Abstract/Free Full Text]
  70. Leone DP, Genoud S, Atanasoski S, Grausenburger R, Berger P, Metzger D, Macklin WB, Chambon P, and Suter U. Tamoxifen-inducible glia-specific Cre mice for somatic mutagenesis in oligodendrocytes and Schwann cells. Mol Cell Neurosci 22: 430–440, 2003.[CrossRef][ISI][Medline]
  71. Lewandoski M. Conditional control of gene expression in the mouse. Nat Rev Genet 2: 743–755, 2001.[CrossRef][ISI][Medline]
  72. Lillioja S, Mott DM, Spraul M, Ferraro R, Foley JE, Ravussin E, Knowler WC, Bennett PH, and Bogardus C. Insulin resistance and insulin secretory dysfunction as precursors of non-insulin-dependent diabetes mellitus. Prospective studies of Pima Indians. N Engl J Med 329: 1988–1992, 1993.[Abstract/Free Full Text]
  73. Marks JL, Porte D Jr, Stahl WL, and Baskin DG. Localization of insulin receptor mRNA in rat brain by in situ hybridization. Endocrinology 127: 3234–3236, 1990.[Abstract]
  74. Martin BC, Warram JH, Krolewski AS, Bergman RN, Soeldner JS, and Kahn CR. Role of glucose and insulin resistance in development of type 2 diabetes mellitus: results of a 25-year follow-up study. Lancet 340: 925–929, 1992.[CrossRef][ISI][Medline]
  75. Medici F, Hawa M, Ianari A, Pyke DA, and Leslie RD. Concordance rate for type II diabetes mellitus in monozygotic twins: actuarial analysis. Diabetologia 42: 146–150, 1999.[CrossRef][ISI][Medline]
  76. Michael MD, Kulkarni RN, Postic C, Previs SF, Shulman GI, Magnuson MA, and Kahn CR. Loss of insulin signaling in hepatocytes leads to severe insulin resistance and progressive hepatic dysfunction. Mol Cell 6: 87–97, 2000.[CrossRef][ISI][Medline]
  77. Mittal V. Improving the efficiency of RNA interference in mammals. Nat Rev Genet 5: 355–365, 2004.[ISI][Medline]
  78. Mokdad AH, Bowman BA, Ford ES, Vinicor F, Marks JS, and Koplan JP. The continuing epidemics of obesity and diabetes in the United States. JAMA 286: 1195–1200, 2001.[Abstract/Free Full Text]
  79. Moller DE and Berger JP. Role of PPARs in the regulation of obesity-related insulin sensitivity and inflammation. Int J Obes Relat Metab Disord 27, Suppl 3: S17–S21, 2003.[CrossRef]
  80. Muoio DM, MacLean PS, Lang DB, Li S, Houmard JA, Way JM, Winegar DA, Corton JC, Dohm GL, and Kraus WE. Fatty acid homeostasis and induction of lipid regulatory genes in skeletal muscles of peroxisome proliferator-activated receptor (PPAR) {alpha} knock-out mice. Evidence for compensatory regulation by PPAR {delta}. J Biol Chem 277: 26089–26097, 2002.[Abstract/Free Full Text]
  81. Nakae J, Kitamura T, Silver DL, and Accili D. The forkhead transcription factor Foxo1 (Fkhr) confers insulin sensitivity onto glucose-6-phosphatase expression. J Clin Invest 108: 1359–1367, 2001.[CrossRef][ISI][Medline]
  82. Nakae J, Biggs WH 3rd, Kitamura T, Cavenee WK, Wright CV, Arden KC, and Accili D. Regulation of insulin action and pancreatic ß-cell function by mutated alleles of the gene encoding forkhead transcription factor Foxo1. Nat Genet 32: 245–253, 2002.[CrossRef][ISI][Medline]
  83. Newman B, Selby JV, King MC, Slemenda C, Fabsitz R, and Friedman GD. Concordance for type 2 (non-insulin-dependent) diabetes mellitus in male twins. Diabetologia 30: 763–768, 1987.[ISI][Medline]
  84. Norris AW, Chen L, Fisher SJ, Szanto I, Ristow M, Jozsi AC, Hirshman MF, Rosen ED, Goodyear LJ, Gonzalez FJ, Spiegelman BM, and Kahn CR. Muscle-specific PPAR{gamma}-deficient mice develop increased adiposity and insulin resistance but respond to thiazolidinediones. J Clin Invest 112: 608–618, 2003.[CrossRef][ISI][Medline]
  85. Okamoto H, Nakae J, Kitamura T, Park BC, Dragatsis I, and Accili D. Transgenic rescue of insulin receptor-deficient mice. J Clin Invest 114: 214–223, 2004.[CrossRef][ISI][Medline]
  86. Patti ME, Sun XJ, Bruening JC, Araki E, Lipes MA, White MF, and Kahn CR. 4PS/insulin receptor substrate (IRS)-2 is the alternative substrate of the insulin receptor in IRS-1-deficient mice. J Biol Chem 270: 24670–24673, 1995.[Abstract/Free Full Text]
  87. Perseghin G, Scifo P, De Cobelli F, Pagliato E, Battezzati A, Arcelloni C, Vanzulli A, Testolin G, Pozza G, Del Maschio A, and Luzi L. Intramyocellular triglyceride content is a determinant of in vivo insulin resistance in humans: a 1H-13C nuclear magnetic resonance spectroscopy assessment in offspring of type 2 diabetic parents. Diabetes 48: 1600–1606, 1999.[Abstract]
  88. Petersen KF, Befroy D, Dufour S, Dziura J, Ariyan C, Rothman DL, DiPietro L, Cline GW, and Shulman GI. Mitochondrial dysfunction in the elderly: possible role in insulin resistance. Science 300: 1140–1142, 2003.[Abstract/Free Full Text]
  89. Previs SF, Withers DJ, Ren JM, White MF, and Shulman GI. Contrasting effects of IRS-1 versus IRS-2 gene disruption on carbohydrate and lipid metabolism in vivo. J Biol Chem 275: 38990–38994, 2000.[Abstract/Free Full Text]
  90. Puigserver P, Rhee J, Donovan J, Walkey CJ, Yoon JC, Oriente F, Kitamura Y, Altomonte J, Dong H, Accili D, and Spiegelman BM. Insulin-regulated hepatic gluconeogenesis through FOXO1-PGC-1{alpha} interaction. Nature 423: 550–555, 2003.[CrossRef][Medline]
  91. Rangwala SM and Lazar MA. Peroxisome proliferator-activated receptor {gamma} in diabetes and metabolism. Trends Pharmacol Sci 25: 331–336, 2004.[CrossRef][Medline]
  92. Sauer B. Functional expression of the cre-lox site-specific recombination system in the yeast Saccharomyces cerevisiae. Mol Cell Biol 7: 2087–2096, 1987.[Abstract/Free Full Text]
  93. Sauer B, Whealy M, Robbins A, and Enquist L. Site-specific insertion of DNA into a pseudorabies virus vector. Proc Natl Acad Sci USA 84: 9108–9112, 1987.[Abstract/Free Full Text]
  94. Schonig K, Schwenk F, Rajewsky K, and Bujard H. Stringent doxycycline dependent control of CRE recombinase in vivo. Nucleic Acids Res 30: e134, 2002.[Abstract/Free Full Text]
  95. Seibler J, Zevnik B, Kuter-Luks B, Andreas S, Kern H, Hennek T, Rode A, Heimann C, Faust N, Kauselmann G, Schoor M, Jaenisch R, Rajewsky K, Kuhn R, and Schwenk F. Rapid generation of inducible mouse mutants. Nucleic Acids Res 31: e12, 2003.[Abstract/Free Full Text]
  96. Shimomura I, Bashmakov Y, Ikemoto S, Horton JD, Brown MS, and Goldstein JL. Insulin selectively increases SREBP-1c mRNA in the livers of rats with streptozotocin-induced diabetes. Proc Natl Acad Sci USA 96: 13656–13661, 1999.[Abstract/Free Full Text]
  97. Streicher R, Kotzka J, Muller-Wieland D, Siemeister G, Munck M, Avci H, and Krone W. SREBP1 mediates activation of the low density lipoprotein receptor promoter by insulin and insulin-like growth factor-I. J Biol Chem 271: 7128–7133, 1996.[Abstract/Free Full Text]
  98. Terauchi Y, Iwamoto K, Tamemoto H, Komeda K, Ishii C, Kanazawa Y, Asanuma N, Aizawa T, Akanuma Y, Yasuda K, Kodama T, Tobe K, Yazaki Y, and Kadowaki T. Development of non-insulin-dependent diabetes mellitus in the double knockout mice with disruption of insulin receptor substrate-1 and ß cell glucokinase genes. Genetic reconstitution of diabetes as a polygenic disease. J Clin Invest 99: 861–866, 1997.[ISI][Medline]
  99. Tsien JZ, Chen DF, Gerber D, Tom C, Mercer EH, Anderson DJ, Mayford M, Kandel ER, and Tonegawa S. Subregion- and cell type-restricted gene knockout in mouse brain. Cell 87: 1317–1326, 1996.[CrossRef][ISI][Medline]
  100. United States Centers for Disease Control and Prevention. Diabetes Fact Sheet. Silver Spring, MD: United States Department of Health and Human Services, 2003; http://www.cdc.gov/diabetes/pubs/pdf/ndfs_2003.pdf
  101. Wang ND, Finegold MJ, Bradley A, Ou CN, Abdelsayed SV, Wilde MD, Taylor LR, Wilson DR, and Darlington GJ. Impaired energy homeostasis in C/EBP {alpha} knockout mice. Science 269: 1108–1112, 1995.[Abstract/Free Full Text]
  102. Yamauchi T, Kamon J, Waki H, Murakami K, Motojima K, Komeda K, Ide T, Kubota N, Terauchi Y, Tobe K, Miki H, Tsuchida A, Akanuma Y, Nagai R, Kimura S, and Kadowaki T. The mechanisms by which both heterozygous peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) deficiency and PPAR{gamma} agonist improve insulin resistance. J Biol Chem 276: 41245–41254, 2001.[Abstract/Free Full Text]
  103. Zhang J, Fu M, Cui T, Xiong C, Xu K, Zhong W, Xiao Y, Floyd D, Liang J, Li E, Song Q, and Chen YE. Selective disruption of PPAR{gamma} 2 impairs the development of adipose tissue and insulin sensitivity. Proc Natl Acad Sci USA 101: 10703–10708, 2004.[Abstract/Free Full Text]
  104. Zisman A, Peroni OD, Abel ED, Michael MD, Mauvais-Jarvis F, Lowell BB, Wojtaszewski JF, Hirshman MF, Virkamaki A, Goodyear LJ, Kahn CR, and Kahn BB. Targeted disruption of the glucose transporter 4 selectively in muscle causes insulin resistance and glucose intolerance. Nat Med 6: 924–928, 2000.[CrossRef][ISI][Medline]




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